1. Technical Field
The present invention relates to a method for processing porcine cornea, and more particularly to a method for processing porcine cornea for decellularization.
2. Related Art
The cornea is an organ refracting light, which accounts for one-sixth of the outermost tunic of the eyeball. The cornea is comprised of a total of five layers, i.e., corneal epithelium, Bowman's membrane, corneal stroma (also substantia propria), Descemet's membrane and corneal endothelium. The corneal epithelium consists of five to six layers of cells. The basal cells of the corneal epithelium arise from stem cells at the limbus, migrate towards the centre of the cornea and are exfoliated in seven days. The Bowman's membrane is composed of acellular collagen fibers and is colorless and transparent. However, the Bowman's membrane cannot be regenerated, scarring normally occurs upon surgical operation or traumatic injury. The corneal stroma makes up approximately 90% of the thickness of the cornea and has uniformly arranged cells with a uniform size. Descemet's membrane consists of three to four layers of cells and is considered to be the base membrane for the corneal endothelial cells. The corneal endothelium is a monolayer of cells, is composed of specialized endothelial cells, is extremely restricted in terms of regeneration, and its cell number decreases with age. When the number of cells decreases, the cells increase in size to fill the void.
Meanwhile, corneal blindness, which results from loss of corneal transparency, is a major cause of vision loss, second only to cataracts. Ocular trauma and corneal ulceration annually blind 1.5 to 2 million individuals. The only efficient treatment for such blindness is transplantation of human donor corneas (also called “keratopasty”). A shortage of donor corneas has brought about the need for an alternative to allograft.
A great deal of research has been conducted into corneal replacements. Synthetic replacement materials include keratoprostheses and natural corneal materials which are tissue-engineered using cultured cells and extracellular matrix (ECM).
However, at present, these materials are not commonly used due to problems associated with biocompatibility and optical and mechanical properties, and xenograft utilizing other animal corneas instead of human corneas is the fastest growing method.
Porcine corneas are the most promising replacement for human corneas, because they have a refractive index and size comparable to human corneas, the use of porcine for transplantation is regarded as ethically acceptable and genetically-modified pigs (e.g., α-1,3-galactosyltransferase knockout pigs and hDAF transgenic pigs) have been developed and are finally entering into clinical practice.
However, conventional research reports that corneal full-thickness xenografts induce severe immune rejection. In addition, research reported by the present inventors showed that lamellar corneal xenografts in the absence of the corneal endothelium still encountered immune rejection [Oh, J. Y., Kim, M. K., Wee, W. R. Lamellar corneal pig-to-rabbit xenotransplantation. Xenotransplantation 15, 198, 2008; Oh, J. Y., Kim, Ko, J. H., Lee, H. J., Park, C. G., Kim, S. J., Wee, W. R., Lee, J. H. Histological differences in full-thickness versus lamellar corneal pig-to-rabbit xenotransplantation. Vet Ophthalmol 12, 78, 2009]. This means that keratocytes (corneal stromal cells) may also cause immune rejection.
Accordingly, the inventors of the present invention considered that acellular porcine corneal stroma (that has been deprived of cells) may be useful as a donor tissue for lamellar corneal xenograft in patients who have normal endothelial cells but suffer from stromal opacities. Furthermore, the recent paradigm of corneal transplantation has changed from full-thickness corneal grafting, in which the overall area is replaced, to partial-thickness corneal grafting, in which only the diseased area is replaced. Such access is regarded as more useful for clinical practice.
A great deal of acellular biological materials is used to repair defects in various organs and various decellularization methods are researched.
However, in-depth research has not been conducted on methods for decellularizing corneal stroma, and in particular, research has not been made on methods for efficiently processing corneas, while minimizing immune responses and pathogenicity after transplantation and maintaining corneal transparency.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.